To determine the relation of a single healed myocardial infarct to a fatal acute myocardial infarct we studied 129 patients at necropsy with 1 grossly visible healed and 1 grossly visible acute infarct, and determined whether the acute infarct was opposite to or adjacent to the healed infarct or if one infarct was so large that it was both opposite to and adjacent to the other infarct. In 74 (57%) of the 129 patients, the 2 infarcts were opposite one another, in 40 (31%) they were adjacent, and in 15 (12%) they were both opposite and adjacent. The age, sex, mean size of the healed infarct and heart weight were similar among the 3 groups. Acute myocardial infarcts were larger in the group that had both opposite and adjacent infarcts than either of the other 2 groups (P<0.001). Information regarding whether the infarcts were clinically recognized or not was available in 108 patients: both infarcts were recognized in 41 (38%), neither infarct was recognized in 15 (14%), and 1 infarct was recognized and the other was not in 52 (48%). The number of the 4 major epicardial coronary arteries narrowed at some point >75% in cross-sectional area by atherosclerotic plaque was similar in patients with recognized and in those with unrecognized infarcts. Similar numbers of narrowed major epicardial coronary arteries also were found in each of the 3 infarct groups (opposite, adjacent or both).